before i made my new hood(pictures soon to come) it would flux between 78-82 so i added some fans and now it has sayed at 79 which is exactly where i want it. fish live longer in colder water temps because their metabolism slows down and the hotter the water the faster it goes which means they need more food and defecate more thus fouling the water. 77 is still a bit low a lot of experts recommend about 78-80 so i hit the middle to 79 and everything stays happy and healthy.